1. Field of the Invention
This invention relates to an improved process for increasing efficiency in the production of nitrated diphenylethers. In particular, it is directed to a process for recovering diphenylether reactants from their nitrated by-products.
2. Description of the Prior Art
The prior art discloses a wide range of diphenylether compounds useful as herbicides. Such diphenylethers are of the structural formula ##STR6## and salts thereof, wherein J is ##STR7##
R.sup.1 is a fluorine, chlorine, bromine, or iodine atom or a trifluoromethyl group;
R.sup.2 is a hydrogen, fluorine, chlorine, bromine or iodine atom or a trifluoromethyl group;
R.sup.3 is a hydrogen, fluorine, chlorine, bromine or iodine atom, or a C.sub.1 -C.sub.4 alkyl, trifluoromethyl, or cyano group;
X is ##STR8##
R.sup.4 is R.sup.5 or an acyl radical of the formula ##STR9## wherein Alk is a C.sub.1-6 alkyl group;
R.sup.5 is a hydrogen atom or a C.sub.1-6 alkyl group optionally substituted with either one or more halogen atoms or a phenyl group;
B is a C.sub.1-10 alkyl, OR.sup.7 or SR.sup.7 ;
y is 1 to 4;
R.sup.6 is a hydrogen atom or a C.sub.1-2 alkyl group;
R.sup.7 is hydrogen, or a C.sub.1-8 alkyl or C.sub.3-8 cycloalkyl group, an agronomically acceptable cationic salt, or a ##STR10## wherein n is 0 t 3
Z is selected from the group consisting of a halogen atom or a C.sub.1-10 alkyl or C.sub.1-10 alkoxy group, cyano, nitro, and trifluoromethyl group; and
R.sup.8 is R.sup.5 or a C.sub.1-6 alkoxy group. Particularly effective as herbicides are those compounds disclosed in U.S. Pat. Nos. 4,031,131, 4,285,723, 4,424,393 and 4,400,530 wherein
A. PA0 B. PA0 1. reduction of the nitro to amino groups; PA0 2. diazotization of the resulting amino groups and replacement of the diazonium group by hydrogen to regenerate the starting compound (II) for the nitration reaction.
R.sup.1 is a chlorine atom or a trifluoromethyl group;
R.sup.2 is a hydrogen or fluorine atom
R.sup.3 is a chlorine atom; and
X is --OR.sup.4 or NR.sup.6 SO.sub.2 R.sup.8 wherein
R.sup.4 is a hydrogen atom;
R.sup.6 is a hydrogen atom; and
R.sup.8 is methyl or ethyl.
Especially preferred are the compounds wherein
(i) X is --OR.sup.4 ; R.sup.1 is --CF.sub.3 ; R.sup.2 is --H; R.sup.3 is--Cl; and R.sup.4 is hydrogen; PA1 (ii) X is --OR.sup.4 ; R.sup.1 is --CF.sub.3 ; R.sup.2 is --F; R.sup.3 is--Cl; and R.sup.4 is hydrogen; PA1 (iii) X is --NR.sup.6 SO.sub.2 R.sup.8 ; R.sup.1 is --CF.sub.3 ; R.sup.2 is --H or --F; R.sup.3 is --Cl; R.sup.6 is --H and R.sup.8 is --CH.sub.3, PA1 (iv) X is --NR.sup.6 SO.sub.2 R.sup.8 ; R.sup.1 is --CF.sub.3 ; R.sup.2 is --H or --F; R.sup.3 is --Cl; R.sup.6 is --H; and R.sup.8 is --C.sub.2 H.sub.5.
R.sup.1 is a halogen atom or a trifluoromethyl group;
R.sup.2 is hydrogen or halogen;
R.sup.3 is hydrogen, halogen, cyano, trifluoromethyl, or a C.sub.1-4 alkyl group X is ##STR11##
y is 1;
R.sup.4 is selected from the group consisting of hydrogen, C.sub.1-4 alkyl, and hydroxy alkyl (C.sub.1-4);
B is SR.sup.7 or --OR.sup.7 ;
R.sup.7 is hydrogen, or a C.sub.1-8 alkyl group, a C.sub.3-8 cycloalkyl group or an agronomically acceptable cationic salt, or a ##STR12## wherein n is 0 to 3 and Z is selected from the group consisting of halogen, a C.sub.1-10 alkyl or alkoxy group, cyano, nitro, and trifluoromethyl.
Particularly effective are those compounds wherein ##STR13##
y is 1;
B is --OR.sup.7, R.sup.7 is --C.sub.2 H.sub.5, R.sup.4 is either --H or --CH.sub.3 ;
R.sup.1 is trifluoromethyl;
R.sup.3 is chlorine; and
R.sup.2 is H.
The compounds represented by formula (I) are produced by the following reaction sequence; ##STR14## wherein J and X are the substituents recited above.
Any nitration technique conventional in the art may be employed. Exemplary of nitration conditions are those disclosed in U.S. Pat. Nos. 4,285,723; 4,031,131; and 4,400,530. In general this nitration reaction is carried out at a temperature of about 0.degree. to about 70.degree. C. in the presence of an electrophilic nitrating agent. While any conventional nitrating agent may be used, preferred are nitric acid/sulfuric acid, potassium nitrate/sulfuric acid or nitric acid/sulfuric acid/acetic anhydride. An inert organic solvent, i.e., a solvent inert to the reactants as well as the nitrated products, can also be used. Exemplary of inert organic solvents are C.sub.5 -C.sub.12 aliphatic hydrocarbons; C.sub.5 -C.sub.7 cyclic aliphatic hydrocarbons; and C.sub.1 -C.sub.6 halogenated aliphatic hydrocarbons. Some examples of suitable solvents are diethyl ether, cyclohexane, hexane, heptane, methylene chloride, ethylene dichloride, chloroform, and perchloroethylene. A chlorinated hydrocarbon is particularly preferred and especially methylene dichloride, ethylene dichloride, chloroform and perchloroethylene. Most preferably, the nitration proceeds in concentrated nitric acid (90-100%) with a mole ratio of nitric acid to reactant (II) between about 5-20 to 1.
Generally, 50-80% by weight of the final product is of structural formula (I) and 20-50% by weight are the nitrated by-products, represented by the structural formula ##STR15## A method of recovering the product represented by the formula (II) is therefore desired.